It is known (allowed U.S. patent application Ser. No. 846,098 filed Oct. 27, 1977 and now U.S. Pat. No. 4,129,594 of J. T. Baker et al. for "Process for the Manufacture of Aromatic Dicarboxylic Acid Chlorides") that said dichlorides can be prepared in very high yield and purity from the corresponding dicarboxylic acids by action of an inorganic acid chloride such as phosgene in a medium of weak tertiary nitrogen base/chlorinated paraffinic hydrocarbon solvent, especially pyridine/dichloromethane. The resulting dichloride can be isolated in pure form prior to use or can be added as the slurry containing dissolved dichloride and slurried hydrochloride salt of the base employed, to a solution (in weak base/solvent medium) of a dihydric phenol for production of polyesters of the aromatic dicarboxylic acids and the dihydric phenols.
To such polyester, in the form of low molecular weight oligomers in solution, a reactive precursor of carbonate formation such as phosgene can be added to produce poly(ester-carbonate), in particular the poly(ester-carbonate) consisting of bisphenol A, terephthaloyl chloride and carbonate units. (Such process is more particularly disclosed in U.S. patent application Ser. No. 764,623 of Prevorsek et al. filed Feb. 1, 1977 and now U.S. Pat. No. 4,156,069 and published as West German patent publication DOS No. 2,714,544 of Oct. 6, 1977). Moreover, process conditions have been disclosed capable of producing species of poly(ester-carbonates) from a dihydric phenol, a dicarboxylic acid and a carbonate precursor such as phosgene, using pyridine alone without a diluent as the medium (U.S. Pat. No. 3,169,121 of Feb. 9, 1965 to E. P. Goldberg). The disclosure therein of operative dihydric phenols and operative aromatic and cycloaliphatic dicarboxylic acids is incorporated herein by reference on the basis that we regard all these materials as operative in accordance with the present invention to obtain products with properties at least equal to those obtained from the same starting materials in accordance with said Goldberg disclosure.
The process of the above noted allowed U.S. Application Ser. No. 846,098 for poly(ester-carbonates) via aromatic dicarboxylic acid chlorides involves use of one reaction vessel in which the dichloride is prepared; and a second reaction vessel in which the slurry containing dissolved dichloride is added to a solution, in a chlorinated hydrocarbon solvent containing weak base, of a bisphenol whereby to obtain low molecular weight polyester oligomers, to which phosgene is then added to obtain the desired poly(ester-carbonate). Various bisphenols and aromatic dicarboxylic acids are specifically disclosed for use in that process. Such poly(ester-carbonate), as disclosed in the above cited U.S. Application Ser. No. 764,623 desirably shows viscosity number (i.e. reduced viscosity=specific viscosity/concentration) in the range 0.6-1.0 dL/g at 0.5 g/100 mL concentration in 60:40 by weight phenol:sym--tetrachloroethane and T.sub.g of at least 170.degree. C. and has good transparency, as determined upon plaques produced by compression molding (at 315.degree. C.) having transmission haze value (ASTM D1003) of not over 15%, preferably not over 10%.